1. Field of the Invention
The present invention concerns a prefabricated civil engineering module, its application to the construction of a structure, and the resulting structure such as a river closure, a dam, barrage or weir, a lock chamber wall, coastal works and similar.
The prefabricatd structure concerned by the invention, or a multitubular type, as will be seen, will for greater simplicity be called a "module" in the following description and claims.
2. Description of the Prior Art
It is known that to achieve a closure, in other words a structure set up across a river stretching from one bank to the other in order to raise the water level upstream, a known method consists in dumping rocks simultaneously over the entire width of the river and in progressing from the bottom up to the surface. Then what is known as a horizontal closure is achieved.
It is also known that when such a closure is achieved, the slope of the downstream face of the structure increases with the weight of the rockfill materials used and the result is that the length and volume of the structure decrease under the same conditions.
Furthermore, when a closure is carried out, it is sought to distribute equally the materials over the whole length of the structure in order to avoid the formation of a low point. In effect, the force of erosion increases with water depth and a local lowering of the crest of the structure therefore tends to increase this force of erosion. One is then in the presence of an unstable phenomenon and if the arrival of the materials added to raise the low point takes too long, these materials are washed away and are deposited on the downstream slope, erosion continuing in this case until the downstream slope of the closure structure has become very low. It is then necessary to use a very large quantity of rockfill materials to reestablish the original level of the structure.
Nevertheless, the regular installation over the entire width of a river of very heavy blocks, whether what is involved are natural rockfills or artificial rockfills such as prefabricated concrete blocks, raises great difficulties. In effect, the simultaneous or almost simultaneous routing of heavy rockfill materials over the entire length of the closure line is very difficult to achieve and generally requires the use of very costly intallations.